1. Field of the Invention
The present invention relates to the field of semiconductor processes, and particularly to methods for forming patterns and mask patterns and a method for manufacturing a semiconductor device.
2. Description of the Related Art
With the scaling down of technical processes, it is hard to get finer pitch patterns with current lithography, and double patterning is one of potential schemes with feasibility. Current double patterning techniques focus on LELE (Litho-Etch-Litho-Etch), LFLE (Litho-Freeze-Litho-Etch) and sidewall spacers.
However, with conventional lithography, it is difficult to provide pattern dimensions less than 22 nm, even for expensive and complex double patterning methods.
DSA (Directed self-assembly) techniques have been widely concerned as a possible solution for the problem of forming smaller pitch patterns, in which a block copolymer (BCP) or polymer compounds is deposited on a substrate through, generally, spin coating, and is “directed” to form ordered structures through annealing. DSA is capable of producing small pitch patterns. Under appropriate conditions, blocks of such copolymer phases are separated into micro domains (also called “domains”), during which nanoscale features are formed for different chemical combinations. The capability of forming such kind of features makes block copolymers suitable for nano-patterning and achieving features with smaller characteristic dimensions (CD), and thus capable of constructing features that are difficult to be obtained through conventional lithography.
As a potentially alternative scheme, DSA can improve the resolution limitation of current lithography through producing self assembled nanoscale domains on a substrate, which is provided with existing patterns defined through lithography thereon. This method may control the spatial alignment of a specific self assembled BCP domain through combining the aspects of self assembly and a lithographically defined substrate.
One DSA process is graphoepitaxy, in which self assembly is guided by topographical features of a lithographically pre-patterned substrate. Graphoepitaxy may provide sub-lithographic, self-assembled features having a smaller characteristic dimension than that of pre-patterned features themselves.
FIG. 1A to FIG. 1E schematically show a prior art pattern formation flow of a self-assembly block copolymer through graphoepitaxy.
As shown in FIG. 1A, positive photoresist 113 is exposed through a mask 114, wherein an ARC (Anti-reflection coating)/PS (polystyrene) brush layer 112 and a photoresist layer 113 are formed in sequence on a substrate 111.
As shown in FIG. 1B, after exposing photoresist 113, the exposed areas of photoresist 113 are removed in a developer to expose the brush layer 112 under the photoresist layer.
As shown in FIG. 1C, a polymer thin film 115 containing a block copolymer is coated on the exposed brush layer 112.
As shown in FIG. 1D, domains 116 and 117 composed of different components are formed through the block copolymer's directed self assembly in the polymer thin film 115.
As shown in FIG. 1E, for example, the domain 117 is selectively removed to form a pattern constituted of the domain 116.
Another DSA technique is surface chemical patterning. FIGS. 2A to 2G schematically show a prior art pattern formation flow of a self-assembly block copolymer through surface chemical patterning.
As shown in FIG. 2A, positive photoresist 213 is exposed through a mask 214, wherein an ARC/PS brush layer 212 and a photoresist layer 213 are formed in sequence on a substrate 211.
As shown in FIG. 2B, after exposing photoresist 213, a patterned photoresist layer 213 is formed to expose the brush layer 112 under the photoresist layer.
As shown in FIG. 2C, the exposed brush layer 212 is oxidized to get an oxygenated brush layer 215.
As shown in FIG. 2D, the photoresist layer 213 is removed to expose the patterned brush layer 212.
As shown in FIG. 2E, a polymer thin film 216 containing a block copolymer is coated on the patterned brush layer 212.
As shown in FIG. 2F, the patterned brush layer 212 is employed as a mask to control the directed self assembly of the block copolymer in the polymer thin film 216, so as to form domains 217 and 218 of different components.
As shown in FIG. 2G, for example, the domain 217 is selectively removed to form a pattern constituted of the domain 218.
However, exposure is generally necessary in all DSA techniques in the prior art, in which mask construction and the like are required, resulting in consequential complexity and high cost.